Cells possess a variety of means to integrate the external stimuli to which they are exposed into coordinated cellular responses. Both direct and indirect interactions between the components of signal transduction systems play important roles in these processes. The discovery of sequence motifs that mediate protein- protein interactions, coupled with the availability of protein amino acid sequence data, allows for the identification of putative protein binding pairs. The studies in this grant application arose from our recognition of amino acid sequences within the primary structures of phosphatidylinositol-specific phospholipase C-y (PLC-y) and PLC-p isozymes that conform to consensus sequences of docking motifs/so-called D-domains, for mitogen-activated protein kinases (MAPKs). Our initial studies support the hypothesis that PLC-y and PLC-p isozymes directly interact with MAPKs. In the proposed studies we aim to substantiate the identification of the putative D-domains and to develop cell-permeable pharmacologic tools that can be used to study the role of PLC-MAPK protein-protein interactions in vivo. The long-term goal for this research is to understand the role of PLC-MAPK signal integration in mental health. The proposed studies consist of three aims. Aim 1 is to determine whether the identified D-domain sequences bind MAPKs in vitro. Aim 2 studies will assess the ability of the identified D-domain peptide sequences to block in vitro interactions between MAPKs and their substrates; in addition, we will determine whether modifications that will be used to promote transmembrane delivery of the D-domain peptides in Aim 3 alter their ability to disrupt MAPK-substrate interactions. In Aim 3 we will quantify the delivery of the peptides into synaptoneurosomes, a preparation of sealed vesicles derived from brain. The results obtained from the proposed studies will expand our understanding of mechanisms of signal integration, providing important information about the means through which complex extracellular stimuli are integrated into coordinated cellular responses. In addition, these studies will provide valuable pharmacologic tools that can be used for studying the role of PLC-MAPK interactions in various cellular responses, including plasticity, growth, and differentiation. This, in turn, will aid in our understanding of both normal and aberrant cell functioning. Thus, these studies will have significant impact on several research fields, including neurobiology, cell biology, biochemistry, and cancer biology. [unreadable] [unreadable]